“Containers” in the sense of the invention are in particular cans, bottles, tubes, pouches made of metal, glass and/or plastic, as well as other packaging containers suitable for filling liquid or viscous products for a pressurised filling or for a pressureless filling.
“Printing” in the sense of the invention is to be construed quite generally as the applying of one or more printed images or prints, in particular also multi-colour printed images or prints, to the respective container outer surface and irrespective of the printing method. The printing is carried out preferably using print heads known to the skilled person and working according to the inkjet method, and which are also described in DE 10 2006 001 223 A1. With this method the printing colours or printing inks are applied as fine droplets next to one another and also partly overlapping one another so as to create a multi-colour printed image, specifically in the form of a colour or print layer formed by the printed image or print after the drying or curing of the printing colours. The containers are printed using for example printing colours which are dried or cured by energy input, i.e. heat and/or UV radiation and/or microwave radiation and/or beta radiation and/or electron beams, preferably through crosslinking. This has the disadvantage that the respective print layer cannot be removed from the containers for recycling—or can only be removed with great difficulty—if this layer is otherwise required to display a high adhesion strength during the minimum shelf-life of the filled product and a high resistance to light and weather.
To avoid this disadvantage, a method is also already known (WO 2010/048119) for printing the respective printed image or print layer onto an intermediate or base layer previously applied to the container surface such that an adhesion strength on the container is obtained for the print layer and the intermediate or base layer which is adequate for normal use and for the normal handling of the containers but that for the recycling process the print layer can be detached relatively easily from the container together with the intermediate or base layer. For this it is proposed that the intermediate or base layer is to be also applied in the form of a plurality of at least partly overlapping droplets of the material forming the intermediate or base layer directly onto the container and cured or crosslinked in this form so that the intermediate or base layer only partially adheres to the container outer surface. Such a method is however at the least time-consuming and requires a not inconsiderable design effort and expense.